New Zealand has about 2600 described spider species with many more as yet undescribed.[1] Some 95 per cent are endemic.
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The largest spider in New Zealand is the Nelson cave spider (Spelungula cavernicola) with a 3 centimetres (1.2 in) body length and a leg span of up to 13 centimetres (5.1 in).
The Australian white-tailed spider, first recorded in New Zealand in 1886, has been falsely attributed as the cause of many necrotising spider bites.[2]
The Avondale spider, also from Australia, was accidentally introduced to New Zealand in the early 1920s in shipments of hardwood logs used for railway sleepers.[3] The spiders, which are considered harmless to humans, have been collected for use in at least two films.
Very few New Zealand spiders have bites which can cause significant injury to humans, and of these, only one — the Katipo — is endemic. Katipo bites have been known to cause systemic effects, such as hypertension, seizure, or coma, though no deaths as a result of Katipo bites have been recorded for over 200 years. Its more dangerous close relative, the venomous Australian Redback spider, has established a foothold in some parts of New Zealand, notably in Taranaki and Central Otago.[4]
There are at least four spiders in the genus Dolomedes (the fishing spiders), species which have adapted to hunt on the surface of water.
Two of the fishing spiders are widespread on the two main islands of New Zealand. Dolomedes aquaticus grows up to 7 centimetres (2.8 in) across and specialises in open, unforested riverbanks, and lives under rocks within 5 metres (16 ft) of the river. Another species of similar size, specialising in forested riverbanks, is also widespread on the mainland, but is as yet undescribed. It is known as Dolomedes III or the New Zealand Forest Fishing Spider. The largest of the New Zealand fishing spiders occurs in the Chatham Islands, but has also not yet been named. The fourth species, D. minor, is not restricted to rivers. Known as the Nursery Web Spider, it makes white nursery webs on shrubs, but is still capable of fishing behaviour. Spinning webs and catching fish.
New Zealand Dolomedes species have yellow stripes on each side of their head (cephalothorax), but their overall colouring is adapted to conceal them in their chosen environment. D. aquaticus is the dark grey of the greywacke rocks that line many New Zealand rivers, while D. III has a mottled pattern to match its forest home.
Spider species in New Zealand include: